Prior art discloses many types of construction sets using friction fitted and releasably interengageable elements, straight tube and rod elements, ring and hoop members, and various optional members such as wheels, hubs, pulleys, plates, and figures. U.S. Pat. No. 3,927,489 discloses set using tubes or plates with channels, friction fitted connector stems with receptive slots, and small connector rings; U.S. Pat. No. 3,698,123 discloses set using slotted rods, extension and locking tubes, rings, and wheels; U.S. Pat. No. 3,550,311 discloses set using rod and tube elements with clutching claws at ends, with claws so designed to frictionally hold rod or tube body, or for claws to interlock with each other; U.S. Pat. No. 3,392,480 discloses set featuring a family of resilient toy figurines with arms and legs terminating in coupling members which permit figurines to interengage with each other or to permit them to grasp and hold mating sized rods and rings; U.S. Pat. No. 3,221,439 discloses a specific resilient double clutching connector element for use in frictionally holding small rods or toy logs in assemblies; U.S. Pat. No. 3,115,340 discloses set of relatively large size metal rings or hoops which are frictionally interengaged to form a game play area layout; U.S. Pat. No. 2,959,888 discloses toy figures and elongated "sticks" or links which are arranged to be interlocked with each other in desired configurations.
Prior art of many of U.S. patents cited feature element types with limited assembly applications, and many feature certain elements which can only be used for abstract type assemblies. Except for the one patent which features hoop elements intended for limited game area layout application, use of such relatively large size rings or hoops is generally lacking or not obvious in assembly considerations. In addition, a simple connector element for interengagement of tubular or rod bodies of two hoops, two straight tubes or rods, or a hoop and a tube or rod is generally overlooked. Furthermore, in general, most construction set elements are intended for or limited to relatively small scale assemblies by individuals and are not suitable for group use.
It must be stated that many other types of documented and undocumented frictionally fitted and releasably interengageable elements and construction sets must be considered as prior art, but differences between this group and those of subject invention will become obvious in subsequent disclosure details.